The instant invention relates to the hydrolysis diaryl ethers to form phenolic compounds.
Diaryl ethers are ethers wherein an oxygen atom joins two aryl moieties. Hydrolysis of diaryl ethers yields phenolic compounds which correspond to the two aryl moieties. A current method of hydrolyzing diaryl ethers is by caustic hydrolysis. That method involves contacting the diaryl ether with water in a caustic aqueous solution at 425.degree. C. and 5200 psig. The equipment to practice that process is extremely expensive because of the harsh reaction conditions necessary to effect hydrolysis.
Both ceria (CeO.sub.2) and thoria (ThO.sub.2) are known to catalyze the equilibrium hydrolysis and dehydration of diphenyl oxide and water to phenol and vice versa. Moss, Improvements in and Relating to Hydration and Dehydration processes and to Catalysts therefor, British Patent No. 911,246 (published Nov. 21, 1962)(dealing with thoria) and Fishel et al., "O-Phenylphenol from Phenol: A Two Step Selective Substitution Process," Catalysis in Organic Synthesis 119, 120 (W. Jones ed. 1980) (dealing with ceria). It is further known that ortho-cresol can be dehydrated in the presence of thoria to yield bis-(2-methylphenyl) ether. Sabatier et al., "Preparation Catalytique des Oxydes Phenoliques et des Oxydes Diphenyleniques," 151 Compt. Rend. 492, 493 (1910). However, thoria catalysts are reported to be ineffective for dehydrating phenolic compounds with ortho substituents larger than methyl groups, such as secondary or tertiary alkyl groups. Clark, Synthesis of Ethers, British Patent No. 1,236,389 (June 23, 1971).
What is needed is an improved process for hydrolyzing diaryl ethers having ortho-aromatic substituents to form the corresponding phenolic compounds.